Molecular mechanics (MM2) calculations and cone angles of phosphine ligands

Chin, Mian; Durst, Gregory L.; Head, Simone R.; Bock, Paul L.; Mosbo, J. A.

doi:10.1016/0022-328x(94)80150-9

Cited by 17 publications

(10 citation statements)

References 80 publications

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“…3,4 Mosbo and coworkers suggested using Boltzmann weighted cone angles to overcome the problem of multiple conformations solution. 18,19 The significant difference in ligand-repulsive energy between the lowest energy form of P(OPh) 3 (E R = 87 kcal/mol) and a low energy form only 0.70 kcal/mol higher in energy (E R = 66 kcal/mol) suggests the need to consider a Boltzmann weighted set of ligand repulsive energies as likely to be more representative of the effective steric requirement of the ligand. In solution, these two conformers will compete for binding to a reaction center.…”

Section: Resultsmentioning

confidence: 99%

Molecular mechanics-based measures of steric effects: Customized code to compute Ligand repulsive energies

2000

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Section: Resultsmentioning

confidence: 99%

Molecular mechanics-based measures of steric effects: Customized code to compute Ligand repulsive energies

2000

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“…The conformation for the fast-reacting enantiomer is more stable because the lone pair, not the methyl, eclipses the aromatic ring. Such conformations have been previously identified as low-energy conformations (37 …”

Section: Front View Side Viewmentioning

confidence: 99%

Kinetic resolution of sulfoxides with pendant acetoxy groups using cholesterol esterase: substrate mapping and an empirical rule for chiral phenols

Serreqi¹,

Kazlauskas²

1995

Can. J. Chem.

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Sulfoxides are valuable chiral auxiliaries because they direct the formation of carbon~arbon bonds. As a route to enantiomerically pure sulfoxides, we examined hydrolase-catalyzed kinetic resolution by hydrolysis of apendant acetoxy group. Screening hydrolases for the enantioselective hydrolysis of the acetate in 2-(methylsulfiny1)phenyl acetate, lb, identified cholesterol esterase (CE) as the most enantioselective enzyme. The enantiomeric ratio, E, ranged from 10 to 25, favoring the (R) configuration at sulfur. Competing chemical hydrolysis of l b caused the large range in the measured values of E. A small-scale (250 mg) resolution of (2)-l b yielded (S)-lb with >99% ee (1 1 % yield) after recrystallization. Changing the methyl substituent to phenyl or n-butyl did not significantly change the enantioselectivity (E = 10 and 15, respectively), but changing it to a chloromethyl substituent lowered the enantioselectivity slightly (E = 5). Changing the phenyl acetate to a naphthyl acetate (2-(phenylsulfiny1)phenyl acetate vs. 1-(phenylsulfiny1)-2-naphthyl acetate) increased the enantioselectivity from 10 to 19. In all cases CE favored the (R)-sulfoxide. To aid the design of new resolutions with CE, we propose an empirical rule that accounts for the observed enantiopreference of CE toward these 5 sulfoxides and 15 other chiral aryl acetates. This empirical rule uses both the size of the substituents and their conformational preferences to predict which enantiomer reacts faster.Key words: kinetic resolution, lipase, cholesterol esterase, sulfoxides, empirical rule, Resume : Les sulfoxydes sont des auxiliaires chiraux utiles parce qu'ils orientent la formation de liaisons carbone-carbone. Dans le but d'obtenir des sulfoxydes Cnantiomeriquement purs, on a examine la possibilitC d'utiliser une rtsolution cinCtique catalysCe par une hydrolase impliquant l'hydrolyse d'un groupe acCtoxy. Une Cvaluation des hydrolases pour leur capacitt a effectuer l'hydrolyse CnantiosClective de llacCtate de 2-(mCthylsulfinyl)phCnyle, lb, a permis d'identifier 13estCrase de cholestCro1 (CE) comme l'enzyme le plus CnantiosClectif. Le rapport CnantiomCrique, E, vane de 10 a 25 et il favorise la configuration (R) au niveau du soufre. L'hydrolyse chimique compCtitive du composC l b provoque les grandes variations observkes dans les valeurs mesurCes de E. Une rCsolution preparative 5 faible Cchelle (250 mg) du composC (2)-lb conduit, aprks recristallisation, au (S)-lb avec un ee >99% (rendement de 11%). Lorsqu'on change le substituant de mCthyle 2 phCnyle ou n-butylC, il n'y a pas de changement significatif d'CnantiosClectivitC (E = 10 et 15, respectivement); toutefois, si on le remplace par un chloromCthyle, 1'CnantiosClectivitC est 1Cgkrement diminuCe (E = 5). Si l'on remplace I'acttate de phCnyle par 1'acCtate de naphtyle (acCtate de 2-(phCnylsulfiny1)phtnyle vs. acetate de 1-(phCnylsulfiny1)-2-naphtyle) 1'CnantiosClectivitC passe de 10 a 19. Dans tous les cas, la CE favorise le (R)-sulfoxyde. Dans le but d'aider au dtveloppement de...

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“…The impact of conformational variations was evoked early [21], leading to use weighted average cone angles [22], while it was considered that this problem was overcome by the use of the solid angle methodology [23]. At the same time, Mü ller and Mingos noticed also that the Tolman cone angle definition does not take into account the variations due to conformational changes [24,25], and they used the atomic centers of the ligand atoms rather than their van der Waals spheres.…”

Section: Introductionmentioning

confidence: 99%

Analytical algorithms for ligand cone angles calculations. Application to triphenylphosphine palladium complexes

Petitjean

2015

Comptes Rendus. Chimie

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Mots cle´s : Angle conique de Tolman Angle conique de ligand Cône minimal englobant Meilleur cône moyen d-dimensionnel Moindre carré s Indice de conicité A B S T R A C TWe defined the smallest enclosing cone angle as the Tolman cone angle for null atomic spheres radii. Then we provide a simple analytical algorithm to compute the smallest enclosing cone at fixed apex, which works in the case of unsymmetrical ligand. We applied it to compute ligand cones for a family of triphenylphosphine palladium complexes, and we showed that both the angle of the cone and its resulting solid angle strongly correlate with the Tolman cone angle, thus suggesting that there is no more need for atomic radii. We also defined the best cone of fixed apex fitting a population of unit vectors. We proposed a simple analytical algorithm to compute it, which is proved to work in any ddimensional Euclidean space. We defined the conicity index k to evaluate quantitavely the pertinence of the best fitting cone. We used this best fit cone to define a mean ligand cone, and thus a mean cone angle and a mean cone axis. We applied it to our family of triphenylphosphine palladium complexes and we observed that the axis of the individual cones deviated from the mean cone axis by at most 13.28. The observed conicity index was small k ¼ 0:0177 ð Þ, indicating a very good fit for the whole family of complexes. ß 2015 Acadé mie des sciences. Published by Elsevier Masson SAS. All rights reserved. R É S U M ÉNous dé finissons l'angle du plus petit cô ne englobant comme é tant l'angle conique de Tolman à rayons atomiques nuls. Puis, nous fournissons un algorithme analytique simple de calcul du plus petit cô ne englobant à apex fixé , qui fonctionne dans le cas des ligands non symé triques. Nous l'appliquons aux cônes de ligands pour une famille de complexes palladium triphenylphosphine et nous montrons qu'à la fois l'angle du cô ne et l'angle solide qui en ré sulte sont fortement corré lé s avec l'angle conique de Tolman, suggé rant ainsi qu'il n'y a plus besoin des rayons atomiques. Nous dé finissons aussi le meilleur cône moyen d'apex fixé pour une population de vecteurs unitaires. Nous proposons un algorithme analytique simple pour le calculer, que nous prouvons être valide dans tout espace euclidien d-dimensionnel. Nous dé finissons l'indice de conicité k pour é valuer quantitativement la pertinence du meilleur cône. Nous utilisons ce meilleur cô ne pour dé finir un cô ne moyen de ligand, et donc un angle moyen de cône et un axe moyen de cô ne. Nous l'appliquons à notre famille de complexes palladium triphenylphosphine et nous

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Molecular mechanics (MM2) calculations and cone angles of phosphine ligands

Cited by 17 publications

References 80 publications

Molecular mechanics-based measures of steric effects: Customized code to compute Ligand repulsive energies

Molecular mechanics-based measures of steric effects: Customized code to compute Ligand repulsive energies

Kinetic resolution of sulfoxides with pendant acetoxy groups using cholesterol esterase: substrate mapping and an empirical rule for chiral phenols

Analytical algorithms for ligand cone angles calculations. Application to triphenylphosphine palladium complexes

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